Windows Server 2016 Webinar

Windows Server 2016
what is new in DNS (and IPv6 and DHCP)
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© Men & Mice http://menandmice.com
Windows Server 2016
DNS Policies
Application Load-Distribution with DNS
IPv6 Root-Hints
DANE-Records Support
Support for Unknown DNS Records
Response-Rate-Limiting
Other new Features in Windows Server 2016
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the features discussed here are based on the  
Technical Preview 5 (April 2016)

DNS Policies
DNS policies give fine control about how DNS queries should
be answered by a DNS server
• similar, but more powerful, than BIND 9 views
• Use-cases
• access control for DNS resolvers (prevent open resolver)
• DNS based load-distribution
• blackholing malicious clients
• Filter based on DNS domains or Query-Type
• Geo-Location-Aware DNS answers
• Traffic-Engineering based on time-of-day
• "Split-Brain" DNS configurations (CAUTION!)
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DNS Policies
Every DNS zone can have one or more
"ZoneScopes"
• each ZoneScope can contain different DNS data (e.g.
different IP-Addresses for the same name)
• the DNS Policy defines, which ZoneScope is used when a
DNS query reaches the DNS server
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DNS Policy criteria
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Client Subnet Source address of the query
Transport Protocol either UDP or TCP
Internet Protocol either IPv4 or IPv6
Server Interface IP address
on which interface the query
comes in
domain name an FQDN (wildcards possible)
Query Type
the requested DNS record type
(A/AAAA/MX/SRV etc)
Time of Day Time when the query is received

DNS Policies
DNS Policy criteria can be combined with boolean
expressions ("AND", "OR", "NOT")
Powerful DNS policies are possible …
… that should be used carefully
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DNS Policies Demo 1
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restricting DNS  
recursion to subnets

DNS Policies Demo 1
Get-DnsServerRecursionScope -Name . 
Set-DnsServerRecursionScope -Name . -EnableRecursion $False 
Add-DnsServerRecursionScope -Name "Clients" -EnableRecursion $True
 
Add-DnsServerClientSubnet -Name "MyNetwork" `
-IPv4Subnet "172.22.1.0/24"
!
Add-DnsServerQueryResolutionPolicy -Name "ResolverPolicy" ` 
-Action ALLOW -ApplyOnRecursion -RecursionScope "Clients" ` 
-ClientSubnet "EQ,MyNetwork"
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DNS Policies Demo 2
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Application load distribution using DNS

DNS Policies Demo 2
Add-DnsServerZoneScope -ZoneName example.com -Name "scope1" 
Add-DnsServerZoneScope -ZoneName example.com -Name "scope2" 
Get-DnsServerZoneScope -ZoneName example.com
!
Add-DnsServerResourceRecord -A -Name www -ZoneName example.com -IPv4Address 192.0.2.10 ` 
-ZoneScope "scope1" 
Add-DnsServerResourceRecord -A -Name www -ZoneName example.com -IPv4Address 192.0.2.20 ` 
-ZoneScope "scope2"
 
Add-DnsServerQueryResolutionPolicy -Name "Scope1LDPolicy" -ZoneName example.com ` 
-ZoneScope "scope1,4;scope,2" -Action ALLOW -ServerInterfaceIP "EQ,172.22.1.150"
!
Get-DnsServerQueryResolutionPolicy -ZoneName example.com
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IPv6 root hints
Windows Server 2016 now comes with IPv6 root-
hints preconfigured
• root hints are required for every DNS server to find the
start of all DNS resolution
• Windows Server up to Windows 2012R2 only contain the
IPv4 root-hints for the Internet (however it was possible to
add the IPv6 root-hints manually)
• This change makes it possible to run the Windows DNS
server in an "IPv6-Only" network
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DANE TLSA Record support
Windows Server 2016 adds support for the TLSA
Resource Record type
• TLSA is required for DANE (DNS Authenticated Named
Entities)
• "pinning" of TLS/SSL certificates via DNSSEC secured DNS
• see our previous webinar "DNSSEC & DANE – E-Mail
security reloaded"  
https://www.menandmice.com/resources/educational-resources/webinars/dnssec-and-dane-e-mail-security-reloaded/
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Demo: TLSA record
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Demo: TLSA Record
Add-DnsServerResourceRecord -Name _25._tcp ` 
-ZoneName example.com -TLSA -CertificateUsage DomainIssuedCertificate ` 
-Selector SubjectPublicKeyInfo -MatchingType Sha256Hash ` 
-CertificateAssociationData 831B809F32A1A9E8C52A5167A35A979F0719B89D08E9A3302264F99D
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Support for "Unknown Resource
Records"
With new protocols, new DNS record types are added to
DNS
•URI
• SMIMEA and OPENPGPKEY
• TA and TALINK
• …
RFC 3597 "Handling of Unknown DNS Resource Record
(RR) Types" defines a way to provision a DNS server with
resource records unknown to the server software
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Support for "Unknown Resource
Records"
the DNS server in Windows 2016 now supports
these unknown resource records
• enables DNS admins to support new protocols which were
not published at the release time of windows server
• the record data is given in hexadecimal notation
• the BIND 9 utility "named-rrchecker" can be used to convert
the data part of an DNS RR into the hexadecimal format
Example: definition of an IPv4 Address "A"-Record:
Add-DnsServerResourceRecord -Name www -ZoneName example.com -Type 1 -RecordData "0A000001"
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Demo: Unknown RRs
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Demo: Unknown RRs
The Uniform Resource Identifier (URI) DNS Resource
Record:
https://tools.ietf.org/html/rfc7553
!
> echo 'IN URI 10 1 "http://www.example.com/path"' | named-rrchecker -u 
CLASS1 TYPE256 # 31 000a0001687474703a2f2f7777772e6578616d706c652e636f6d2f70617468
!
PowerShell> Add-DnsServerResourceRecord -Name _http._tcp -ZoneName example.com ` 
-Type 256 -RecordData "000a0001687474703a2f2f7777772e6578616d706c652e636f6d2f70617468"
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Response Rate Limiting
DNS responses from DNS servers in the Internet
(Authoritative or DNS resolver) can be mis-used for
denial of service attacks
• A problem for a long time, but has been especially popular
with attackers in the last five years
• For additional coverage on this topic, watch our webinar
"The dangers of DNS reflection attacks"  
 
https://www.menandmice.com/resources/educational-resources/webinars/the-dangers-of-dns-reflection-attacks/
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What is the problem
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DNS is UDP "stateless"
communication
source IP addresses can be
spoofed
some DNS
Server in the Internet
Source IP
Address
"spoofed"
Answer is
delivered to the
owner of the
"spoofed" IP
Address

What is the problem
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There are many many DNS
servers to be found in the Internet

One Solution: Response Rate Limiting (RRL)
• RRL was developed by Vernon Schryver and Paul Vixie
and implemented in BIND 9, NSD, Knot and PowerDNS. It
is now also available in Windows Server 2016. 
• as all DNS queries should go through a caching server  
• identical queries should not be seen from the same
source inside the TTL (Time to Live)  
• if the DNS server sees (many) recurring queries within
the TTL, it is likely an attack
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• response rate limiting counts the number of
identical responses sent to a given network 
• will throttle outgoing responses if too much
identical responses are sent 
• allows legit clients in the victims network to still
resolve DNS data
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• in case an attack is detected, (almost) empty
answers are sent with "TC" flag set 
• "TC" flag = answer truncated, retry over TCP 
• real caching DNS server will repeat the query over
TCP (slower, but harder to spoof)
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•RRL enabled on an authoritative server
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Demo: RRL
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Miscellaneous news
DHCP: Network Access Protection (NAP) has been removed
from DHCPv4 in Windows Server 2016
Containers with Docker: lightweight separation of
Applications on a single Windows Server 2016 instance (can be
used to separate a DNS or DHCP server)
Nano-Server: minimal Windows Server 2016 image without
GUI. Can be used to create a lightweight DNS-Server
deployment
Software Defined Networking (SDN) and Layer-4 Load-
Balancer: load-balance DNS server (for example DNS resolver)
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Release Dates
Windows Server 2016 will be released in Q3 2016
Men & Mice Suite 7.3 (September 2016) will
support Windows Server 2016
Many of the new features will be supported in the
Men & Mice GUI and Web-UI
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Upcoming Webinar
June 9th, 2016 - Yeti-DNS
!
Yet-DNS - an international research project  
on the DNS root-server system
Interview with Shane Kerr of BII
How-To participate in Yeti-DNS with a  
DNS resolver
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Thank you!
!
Questions? Comments?
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Windows Server 2016 Webinar

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Windows Server 2016 Webinar